The field of aerodynamic design for projectiles, aircraft, rockets and the like is extensive. The physical size of small caliber bullets/projectiles presents challenges not encountered in aircraft wing, ballistic missile, artillery shell or aircraft delivered bomb design. For small caliber weapons like handguns, shotguns, rifles and machine guns, performance enhancements have for decades been incremental at best.
Hollow tube projectiles have been studied and tested since before WWI but heretofore have demonstrated inferior ballistic performance at mid-range to longer distances. Conventional hollow tube bullets exhibit inferior ballistic performance due to the air not readily passing though the tube as might be expected and results in drastically reduced ballistic efficiency. At speeds not much below Mach 2, the airflow through the hollow tube chokes itself off, increasing aerodynamic drag and reduced range of the projectile. The dramatic performance limitations caused by the choked flow problem can be understood from the Schlieren photographs found in the 2004 presentation Performance Potential for a New Machine Gun and Ammunition Concepts to the US Department of Defense document found at the Defense Technology Information Center web page, www.dtic.mil/ndia/2004solic/flat.ppt. Eliminating the choked flow condition and maintaining the hollow tube bullet's inherent aerodynamic efficiency across the continuum from subsonic through high Mach number velocities is unknown in the art and field of ballistics.
The difference in ballistic efficiency for the projectile diameter used in common handguns and rifles is vast. Handgun projectiles are typically designed for close range and rifles for more distant targets. The different applications affect the overall size of the weapon, bullet shape, bullet diameter, cartridge overall length, magazine capacity and projectile performance. For example, common 30 caliber bullets for handguns have a diameter from 0.309 to 0.312 inches, weigh from 80 to 110 grains and have ballistic coefficients of around 0.100 to 0.150.
Common 30 caliber bullets for rifles have a diameter from 0.303 to 0.311 inches, weigh from 110 to 220 grains and have ballistic coefficients of around 0.250 to 0.450. The lower the ballistic coefficient, the quicker the bullet loses velocity and useful range. Nose profile or shape, ratio of length to diameter, shape of the end of the projectile and other design aspects significantly affect the ballistic coefficient. Typically handgun bullets are larger in diameter than rifle bullets. The 30 caliber cartridges best illustrate the performance variations between handgun and rifle bullets of the same nominal diameter.
The Tokarev handgun cartridge from the Soviet Union, also known as the 7.62×25 mm, commonly has a bullet diameter of 0.309 inches, bullet length of 0.52 inches for a 90 grain weight, case diameter of 0.387 inches, cartridge overall length of 1.34 inches, muzzle velocity of 1400-1700 feet per second from a 4.5 inch barrel, ballistic coefficient of 0.142 and an effective range to 50 meters+/−. The well-known rifle cartridge .308 Winchester, also known as 7.62×51 mm NATO, commonly has a bullet diameter of 0.308 inches, bullet length of 1.15 inches for a 165 grain weight, case diameter of 0.470 inches, cartridge overall length of 2.81 inches, muzzle velocity of 2600-2800 feet per second from a 20 inch barrel, ballistic coefficient of 0.450 and an effective range of 800 meters+/−.
Trying to use lighter weight rifle bullets in a pistol application like the Tokarev results in functional compromises or are simply unworkable. Properly seating a tapered nose, longer bullet can extend the cartridge overall length beyond the physical constraints of the breech or cannibalize case capacity for the propellant needed to move the bullet at desired velocities.